Technique for sensing the rotational speed and angular position of a rotating wheel using a variable threshold
First Claim
1. A method of detecting rotational speed and angular position of a rotating wheel with a non-contact sensor that provides a pulse train output signal, said method comprising:
- comparing the amplitude of the pulses of the pulse train output signal with a first variable switching threshold value to provide an output signal;
receiving the output signal detect a synchronization signal and provide a sync signal indicative thereof; and
adjusting said switching threshold value when the difference between the amplitudes of the pulses and said switching threshold value exceeds a fixable first maximum value and said sync signal is valid.
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Accused Products
Abstract
To detect the rotational speed and angular position of a rotating wheel, a non-contact sensor (e.g., an optical sensor or a Hall sensor) scans scan marks on the wheel, and generates a pulse train. The amplitude of the pulses is compared in a comparator with a variable switching threshold. To achieve accurate measurement results, and to compensate for offset and long-term drift of the sensor, the switching threshold is adjusted if one or more of the following conditions is met: (i) the difference between the pulse amplitude and the switching threshold exceeds a fixable first maximum, (ii) the difference of the amplitudes of two successive pulses exceeds a fixable second maximum, (iii) the difference of the frequencies of successive pulses exceeds a fixable third maximum. The method is particularly advantageous in a motor vehicle, to detect the rotational speed and angular position for an electronic ignition system, or the rotational speed and angular position of the wheels for an ABS braking system, an anti-skid system, or a vehicle stabilization system.
27 Citations
14 Claims
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1. A method of detecting rotational speed and angular position of a rotating wheel with a non-contact sensor that provides a pulse train output signal, said method comprising:
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comparing the amplitude of the pulses of the pulse train output signal with a first variable switching threshold value to provide an output signal;
receiving the output signal detect a synchronization signal and provide a sync signal indicative thereof; and
adjusting said switching threshold value when the difference between the amplitudes of the pulses and said switching threshold value exceeds a fixable first maximum value and said sync signal is valid. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of detecting rotational speed and angular position of a rotating wheel with a non-contact sensor that provides a pulse train output signal, said method comprising:
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comparing the amplitude of the pulses of the pulse train output signal with a variable threshold value to provide an output signal;
receiving the output signal to detect a synchronization signal and provide a sync signal indicative thereof; and
adjusting said variable threshold value to maintain the difference between the amplitudes of the pulses an said variable threshold value less than a first value when said sync signal is valid.
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14. A method of detecting rotational speed of a rotating wheel with a non-contact sensor that provides a pulse train output signal, said method comprising:
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comparing the amplitude of the pulses of the pulse train output signal with a variable threshold value to provide an output signal indicative of rotational speed;
receiving the output signal to detect a synchronization signal and provide a sync signal indicative thereof; and
adjusting said variable threshold value to maintain the difference between the amplitudes of the pulses and said variable threshold value less than a first value when said sync signal is valid.
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Specification